This invention relates to an apparatus for automatically removing an electrode chip from a shank of a resistance welding robot on which the electrode chip is held.
Respective electrode chips on a pair of shanks for a resistance welding robot are required to be periodically replaced by new ones because the electrode chips are worn away due to their repeated use. Thus, the electrode chips should be removed from the corresponding shanks by an electrode chip removing apparatus.
Such electrode chip removing devices have been disclosed by Japanese Patent Application Laying-Open No. 184673/1991 and Japanese Utility Modal Publication No. 3,738/1992, for example.
The device disclosed by Japanese Patent Application Laying-Open No. 184673/1991 is shown in FIGS. 13 and 14. A pair of electrode chips 1 and 1 on respective shanks 2 and 2 for a welding robot gun are moved by the shanks 2 and 2 in a direction in which they move closely to each other to enter recesses 101 and 101 in a remover arm 100. The electrode chips 1 and 1 are held on the remover arm 100 by cams 102 and 102 which are pivotally mounted on the remover arm 100 so that the cams 102 and 102 rotate and bite the electrode chips 1 and 1 as indicated by a dotted line in FIG. 14 so as to securely hold them on the remover arm 100. Thus, when the shanks 2 and 2 are moved in a direction in which they are moved away from each other, the electrode chips 1 and 1 are removed from the shanks 2 and 2 while they are kept to remain in the recesses 101 and 101. The cams 102 and 102 may be rotatably moved by an appropriate driver not shown.
However, according to the chip removing device disclosed by Japanese Patent Application Laying-Open No. 184673/1991, if the electrode chips 1 and 1 are very securely held on the shanks, then it is difficult to remove them from the corresponding shanks 2 and 2. In addition, the cams 102 and 102 tend to deform the end of the shanks 2 and 2 or the robot gun because the cams are forcedly engaged with the electrode chips 1 and 1.
The device disclosed by Japanese Utility Model Publication No. 3738/1992 is shown in FIG. 15. The remover device 200 may be in the form of an arm having a U-shaped end 202 which is disposed between a shoulder 2a of the shank 2 and an upper end 1a of the electrode chip 1 and a pivoting protrusion 202a engaged with the shoulder 2a of the shank 2 so that the remover device 200 can rotate about the pivoting protrusion 202a in a clockwise direction as indicated by an arrow A of FIG. 15. This rotation of the remover device 200 causes the electrode chip 1 to be removed from the shank 2 in a downward direction as viewed in FIG. 15.
However, such a remover device 200 tends to damage the shoulder 2a of the shank 2 as well as the upper end 1a of the electrode chip 1. Furthermore, an axis of the shank 2 will be disadvantageously deformed as indicated by an arrow B of FIG. 15 due to a force applied to the shank 2 as indicated by the arrow B when the electrode chip 1 is removed from the shank 2.